Wild salmons take and accumulate a carotenoid colorant contained in shrimps, prawns, lobsters, or crabs in the natural world, and thus the flesh of the wild salmons exhibits a reddish orange color. Cultivated salmons are usually cultivated with a feed supplemented with a carotenoid colorant in order to allow the flesh thereof to exhibit a color close to that of wild salmons.
As the carotenoid colorant to be supplemented to the feed, a chemically synthesized astaxanthin is conventionally in a wide use (Critical Reviews in Food Science and Nutrition, 46: 185-196 (2006)). Known examples of a naturally occurring carotenoid colorant used for improving the flesh color of salmons include astaxanthin produced by Phaffia rhodozyma (PCT National-Phase Japanese Laid-Open Patent Publication No. 8-508885), astaxanthin produced by alga Haematococcus pluvialis (U.S. Pat. No. 4,871,551), and capsaicin, which is a component of red pepper (Japanese Laid-Open Patent Publication No. 2005-27662). Although not for salmons, it is known to use a carotenoid colorant produced by bacteria Paracoccus carotinifaciens E-396 strain (FERM BP-4283) for testing the color tone improvement on the surface of red sea bream (Japanese Laid-Open Patent Publication No. 9-308481). A substance containing a colorant to be supplemented to the feed, which is formed of a precipitate obtained as a result of microorganism culturing, the precipitate containing a carotenoid compound, is also known (Japanese Laid-Open Patent Publication No. 2001-95500).